Resin compositions, which generally comprise an aromatic polyester and a polycarbonate, are widely used in the industry. Among them, resin compositions comprising a polytrimethylene terephthalate and a polycarbonate have excellent appearance, mechanical properties, heat resistance and dimension properties. Therefore, they are useful as a material in automobile parts, electric/electronic parts, construction parts and industrial parts. In particular, such resin compositions are useful as exterior automobile parts due to their excellent appearance and heat resistance. However, in recent years, heat resistance has become increasingly demanded in this industrial field. In this context, a conventional resin composition comprising a polytrimethylene terephthalate and a polycarbonate provides products with only insufficient high-temperature mechanical properties in the field where such high-temperature mechanical properties are required, e.g., automobile exterior handles or roof legs.
For example, Patent Document 1 discloses a thermoplastic resin composition comprising a polytrimethylene terephthalate and a polycarbonate having melt viscosity stability defined for the purpose of improving wet heat resistance. However, the demanded heat resistance and rigidity when heated are still not satisfied even if this technique is employed. In addition, Patent Document 2 discloses a resin composition comprising a polytrimethylene terephthalate and a polycarbonate, which is characterized in that the polytrimethylene terephthalate contains a specific amount of a dipropylene glycol component to improve wet heat resistance. However, heat resistance and physical properties when heated are still not improved even if this technique is employed.    Patent Document 1: JP-A-2002-265771    Patent Document 2: JP-A-2002-275369